Step 9: Germinating the Seeds

Step 10: Disinfecting and Filling the Reservoir

The Nutrient Reservoir can become quite a utopia for all sorts of nasty microorganisms that can wreak havoc on your plants. If I've only learned one t...

This instructable will cover the build and operation of a deep water culture hydroponics system. So far, I have sucessfully grown banana peppers in this setup with complete ease since most of the process is automated.
Also, these plants were grown indoors completely under artificial light that outputs about 60 watts. The entire unit requires about 65 watts and runs for about 16 hours every 24 hours. It costs about 9 cents a day to run it.
When I first wrote this instructable it was about a month before I planted anything in it. Since then I have made many modifications to the hydroponics system such as a third light and a more advanced electrical system. I'm soon going to make a fabric cover for it with built in fans for air circulation. As a result you'll see some old and new pictures mixed together. Please bear with me untill I find enough time to re-write the whole thing.

Step 1: Warning Science Content: An Introduction to Plant Physiology

To the naked or untrained eye, plants can appear as very simple and boring forms of life. In reality, plants are very complex creatures. In fact, genetically speaking plants are about twice as complex as humans.

They exist in two very separate yet two very interconnected and equally important worlds. There is the above ground world of the shoot system and the underground world of the root system.

The shoot system of the plant is what we normally see when we look at a plant in the ground. From figure 1B you'll notice that the shoot system is extensively branched to allow a maximum surface area for the absorption of sunlight. This part contains the leaves, which is where the chemical reaction we learned in junior high takes place: 6 CO2 + 6 H20 ==> 6 O2 + C6H12O6

This chemical process is known as photosynthesis in which the radiant energy from the sun is harnessed and converted into chemical energy in the form of sugars. Excess sugars produced by the plant can be stored in bulk, usually in the form of a fruit that is meant to provide a developing seed with energy until it can grow it's own leaves and manufacture it's own glucose.

The process of photosynthesis is actually much more complex than the above chemical reaction. It is really a series of dozens of chemical reactions that are only a small part of a plant's overall metabolism, which requires many other nutrients such as Nitrogen, Potassium, and Phosphorus. But how does the plant collect these nutrients? From it's root system.

The root system is responsible for providing the leaves and the rest of the plant with the required raw materials for metabolism and photosynthesis. From figure 1B you'll notice that the root system is extensively branched to allow a maximum surface area for adequate absorption of water and nutrients from the soil. Anything that is absorbed by the roots are transported up to the leaves through the plant's stem. In return, some of the oxygen and sugars produced by the leaves are transported down to the roots through the stem. The roots are not exposed to sunlight and therefore cannot manufacture it's own sugars.

There are three main problems with soil that limit the growth of a plant:One is that soil does not contain a whole lot of oxygen that the roots need to survive. Roots need to "breathe" just like we do and this can cause a lot of problems when oxygen is scarce. Hydroponics systems help with this by delivering a highly oxygenated nutrient solution to the roots. This is most commonly achieved through the use of air pumps and bubblers similar to those used in aquariums.

The second problem with soil it that nutrients are often scarce and in a form not usable by the plant. For example, nitrogen in soil is often in the form of ammonia or gas and must be processed by nitrogen fixing bacteria before the plant can use it. Hydroponics systems suspend the roots directly in a nutrient rich solution that can be readily absorbed by the roots and used for growth.

Finally, soil can contain many pathogens that can lead to diseased plants. Hydroponics solutions can be easily sterilized to prevent any nasty creatures from infecting your plants.

By addressing these three problems, hydroponics allows plants to grow and develop at an accelerated rate. With all that being said, I finally give to you my design of an indoor Deep Water Culture (DWC) hydroponics system.

somehow i never had any good results with rockwool, yes seed germinates but plant has stunted growth, roots just sont seem to grow through it and then after some time of a plant being only 1 inch max long, they just die. I am sure it is something I am doing wrong

Sounds like you might not be feeding them. The rockwool cube is an inert medium and provides the plants with no nutrients. If the nutrient reserve in the seed is all the plant has to survive on it will surely die as you describe. I recommend using a general purpose plant food mixed to 1/2 strength. Soak the cubes in the plant food solution before adding the seeds. Not long after the plant starts to grow secondary leaves you will want to transfer it to your hydroponics system with a reservoir full of good quality nutrients. Thank you for your comments.

Thanks for yr reply, but I have been feeding them a liquid fertilizer and in fact had soaked the cubes in it before as well. Nevertheless, thank you for trying to help. I will just try again, maybe with different fertilizer. I wish they reached the 2nd leaf stage :-)

Just thought I might try give a little info from my experiences with rockwool. Certain types of seeds have issues with growing through the density of the rockwool. I would suggest either to softly loosen up the block after it has been soaked, or use a coconut husk pellet (similar to the peat pellets, but I've found them to be a more neutral medium than the peat). I have not had much issue putting the coconut husk pellet into the clay medium. And depending on the plant variety, you may be able to replace the clay with pond pebbles.

I personally have found that circulating an aquarium's water through the hydroponic reservoir takes care of a basic nutrient-rich water and sometimes even eliminates the need for an aquarium filter.

The exact size of the airspace is not critical. When I first fill the reservoir with fresh solution I leave about 1/2 inch or so. As time goes by, the solution level will go down and the gap will increase. As long as there is an airspace and the roots are in the solution you should be fine. Thanks for your question.

The exact size of the airspace is not critical. When I first fill the reservoir with fresh solution I leave about 1/2 inch or so. As time goes by, the solution level will go down and the gap will increase. As long as there is an airspace and the roots are in the solution you should be fine. Thanks for your question.

Good quality mylar reflects 90 - 95% of visible light, about the same as a common glass miirror. High end, titanium oxide, white paint (on a primed surface) reflects about 90 - 95 % as well. Aluminum foil or polished aluminum panels reflect about 80 - 90% of visible light, as do cheap mylar-like films. Regular flat white paint is in the 80 - 90% range as well. Any of these is a good choice over darker surfaces or open space.

Consumption of nutrients? When to change/add to solution?I have a similar, but smaller system in my office designed to keep my office plants alive, eliminating the need for watering them.

I do however wonder: How to figure out when to add new nutrients to the solution or change the water. I only have 6 plants, but don't really know when they have used up all their nutrients - and i have not been able to find a way of measuring it? I usually just add some more when "I feel it is time" but I don't actually have any basis for making the assumption.What do you guys do?

How do you figure out when to add more solution?Is it better to entirely change the solution? (which i gather would be rather costly if it was a big system)

The two main things you want to watch for in your nutrient solution is the pH and the ppm. The pH refers to the concentration of H3O+ / OH- ions in your solution on a logarithmic scale. The ppm refers to the concentration of other dissolved ions such as potassium, nitrogen and phosphorous in parts-per-million. You can buy a special electrode that you can dip in the solution and it will give you a readout of these two numbers. It looks a lot like a pen. It can cost up to $200 though. Every different plant has its own range of pH values that they grow best in. You should do your own research to see what your own plants need. Generally, the pH of a hydroponics nutrient solution tends to go down over time (gets more acidic). Periodically, you can adjust the pH by adding some "pH down" (usually dilute hydrochloric acid) or "pH up" (usually dilute potassium hydroxide), both chemicals available at any hydroponics store. The ppm of the solution tends to do down over time as well. you can bring it back up to optimal levels by adding more nutrient to your solution. Keep in mind that while the plants are absorbing the nutrient solution, they are also dumping metabolic waste products into it. If you leave the solution too long the waste can rise to toxic levels and kill the plants. It's time to flush the system and start with fresh solution before that happens. I recommend a change every week but you might even make it up to two weeks. It depends on the size of the reservoir and the size/number of plants. Hope that helps!

Use pH indicator drops as a cheap alternative to a pH meter. Different plants like different pH and nutrient mixes, but a pH around 6 and a general purpose vegetative growth nutrient solution will work for most plants until you want want buds/flowers/fruit. Check nutrient concentration (TDS/ppm), feed and check pH frequently. Use foil around the base of the plants to keep light out of your fluids and roots. Unless you are pushing the limit with nutrient concentrations, you can go a couple of months before flushing the system.

Awesome instructable, however, I can't seem to download it. Everytime it tries to load it just gets stuck or quits (times out) on me after 10 mins of nothing. Maybe I should take it up with the Instructables crew rather. What say you?

Im having trouble getting setup for your PRO membership.. I wounder if you can accept checks on line. would appricate hearing from you.. You have a nice site . keep up the good work. espically like your hydroponic s im trying to learn how to grow indoors. Thank You

The wire is pretty stiff and it would have been very hard to feed it through all the 90 degree turns in the pipe. I suppose I could have tied some string to the wires and pulled them through the pipes but then I would have to wire it up before I glued it together. That would make the structure and the wiring ten times harder to complete.

you are wrong with your calculations but within reason your lights would more likely be pulling .23 amps. The reason for that is there is alot more than one calculation you can use to calculate current draw. Because the ballast of the florescent lights you need to use another calculation but you don't have the proper testing tools to actually find the right variables. Your best way to actually find the current draw is to use an ammeter. And just because you use stranded wire DOES NOT mean it can handle more current.

WOW! I am completely impressed! Just starting to investigate hydroponics, you make it seem so simple! ( I am sure that is a "ha-ha"). Where I live, (USA, on west coast, no sun), is in an agriculture belt, but alas, I can't even grow tomatoes...no sun, too many pine trees...So, this seems perfect! If you ever want seeds, I have been collecting organic seeds for many years, have LOTS, and am willing to share. Pumpkins, Italian Butter beans (really good), all the way to pears, apples, persimmons and tangerines. Let me know if you would like any seeds to experiment with. How would fruit trees do in hydroponics?

um...i'm gonna have to say that fruit trees get way too big for hydroponics even before they are ready to bear fruit. I have just purchased 6 seedlings that are about 6 feet high and in 4 gallon planters that won't produce fruit for at least a few years until they are well established in the soil. I guess it's possible on a huge scale, but not practical.